MongoDB allows for field level updates, which enable developers to update individual fields atomically, similar to traditional RDBMS. This feature is crucial in systems like YCSB, where updates can be challenging without it, leading to potential data inconsistencies and lost updates. Field level updates are particularly useful when reads are heavy and writes are infrequent, as they allow for faster reads while maintaining concurrency correctness. The ability to update individual fields also enables techniques like "update if current," which can improve performance in certain scenarios. Overall, MongoDB's field level updates provide a key advantage over other NoSQL systems and key/value stores, enabling developers to write more efficient and scalable code.